In what officials are calling a “freak incident,” one of Brookfield Zoo’s seven dolphins died Monday at about 1 p.m., shortly before it was set to perform for a Labor Day crowd.

According to the zoo pathologist who performed the necropsy, 4-year-old Nea suffered a skull fracture. Zoo officials believe Nea, who was the youngest dolphin in the zoo’s collection, collided with another dolphin.

Sondra Katzen, the zoo’s media relations manager, said the two keepers were sitting downstairs in their office, where the clicks and whistles of the dolphins are broadcast.

“They heard a loud pop,” said Katzen.

Two trainers, noticing something was wrong with Nea, dove into the water to try and revive her. The pair did CPR until veterinarians arrived within 10 minutes. But the dolphin didn’t respond.

“We believe that, upon impact, she died right away,” said Katzen, who added that officials ruled out the possibility of Nea colliding with a wall. There was no information available on whether any other dolphin showed signs of being injured.

Dolphin shows were canceled for the remainder of the day Monday but resumed Tuesday, said Katzen.

Nea came to Brookfield Zoo a year ago from Dolphin Quest in Bermuda, where she was born to a dolphin from Brookfield Zoo that was on loan to that organization.

– Bob Uphues